The latest incident happened in Rohtak district when the two students, 22-year-old Aarti and 19-year-old Pooja, were on their way home.

Younger sister Pooja told BBC Hindi that the three young men "threatened us and abused us".

"The men started to abuse me and touch me. I told them 'if you touch me again, you'll get beaten up'. They called a friend on the phone and told him to 'come over because we have to beat up some girls'," Pooja said.

She said they decided to take on the attackers when other passengers did not come to their help.

"No one came forward in the bus to help us. So we took out our belts in self-defence [and hit the men]. If only the other passengers had helped us, we would not have needed to retaliate in this way," she said.

However, the video of the incident shows at least one male passenger repeatedly trying to separate one of the men from the women.

The sisters said the men pushed them out of the bus when it came to a halt after some distance and attacked them again.

They said they retaliated by throwing a brick at the men who then fled.

Analysis: Geeta Pandey, BBC News, Delhi

Women in India are taught early on in life to develop a thick skin while walking on the streets or using public transport - they are told to ignore catcalls and lewd comments, avoid the predatory male gaze, even move away quietly when a man pinches them on the buttocks or elbows them in the breast.

Any woman growing up or living in India knows the feeling of shame and rage that such harassment causes. But despite being told to take flight - not fight - women across India have been regularly fighting back.

As college students, we grew our nails and carried umbrellas to push back a man who got too close for comfort. Sometimes, a particularly bold friend would slap a man.

But since the 2012 gang rape and murder on a Delhi bus, gender issues have been more in focus and there is a stronger feeling among women today that they won't remain quiet when harassed.

For the sisters, seen in the video fighting men who allegedly teased them and touched them inappropriately, it appeared to be a battle for life and death.

And the women's fight has been brought into the public consciousness by the shocking video - shot reportedly by a pregnant woman on the bus, who despite considerable risk to herself decided to film the whole episode while most other passengers looked the other way.